The present application is directed to beam position detection and control, and more particularly to systems and methods that enable sensing the position of a beam along one or more axes while minimally perturbing or interfering with the beam, and, when appropriate, moving of the beam to control its position.
A number of beam sensing systems and methods are known. One type of system senses the beam itself. For example, in Bhalla et al., U.S. Pat. No. 6,301,402, the main beam is dithered in order to provide appropriate alignment information and control. However, during sensing of beam position, the beam cannot be used normally for its intended purposes. This shortcoming delays or impacts desired operational use of the beam.
Another beam sensing system, U.S. Pat. No. 4,459,690 to Corsover et al. describes a single dithered beam system, where the output from a light source is split by a beam splitter into a plurality of beams. This plurality includes a light beam (PBT) used for tracking a guide track (T) of an optical disc. The tracking is accomplished by dithering the PBT beam that impinges as a light spot (PT) upon guide track (T). The dithered beam (PBT) is used for tracking purposes in both a playback and record mode. In a preferred embodiment, the playback beams are split by an optical grating and dithered by an acousto-optic device. Such a system generates an error signal which is to be driven to zero, but it does not teach measuring the position of a beam over a variable range. Corsover et al., therefore, show a teaching for sensing a relative distance from a track which is a fixed feature. It does not teach sensing of an actual position of a main beam which permits for adjustable control.
Accordingly, a new system which provides highly accurate, highly responsive position sensing and/or control is desirable. The system should provide minimal disturbance of the main beam in its operation, while preferably providing precision sensing and also providing both rapid response and long-term stability. Such a system would be anticipated to have applicability in a variety of beam sensing applications, including that for beam position control. Control of a beam in this manner has applicability in a variety of environments, including laser printing, medical laser systems, precision laser instruments, optical switch networks, free space laser communication, high power lasers, as well as other industrial and academic settings.